The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design.

The Halogen Bond

We review the synthesis of semiconductor nanocrystals/colloidal quantum dots in organic solvents with special emphasis on earth-abundant and toxic heavy metal free compounds. Following the Introduction, section 2 defines the terms related to the toxicity of nanocrystals and gives a comprehensive overview on toxicity studies concerning all types of quantum dots. Section 3 aims at providing the reader with the basic concepts of nanocrystal synthesis. It starts with the concepts currently used to describe the nucleation and growth of monodisperse particles and next takes a closer look at the chemistry of the inorganic core and its interactions with surface ligands. Section 4 reviews in more detail the synthesis of different families of semiconductor nanocrystals, namely elemental group IV compounds (carbon nanodots, Si, Ge), III–V compounds (e.g., InP, InAs), and binary and multinary metal chalcogenides. Finally, the authors’ view on the perspectives in this field is given.

Synthesis of Semiconductor Nanocrystals, Focusing on Nontoxic and Earth-Abundant Materials.

Recent advances in layered double hydroxide-based nanomaterials for the removal of radionuclides from aqueous solution.

Block copolymer thin films can be used as soft templates for a wide range of surfaces where large area patterns of nanoscale features are desired. The cylindrical domains of acid-sensitive, self-assembled monolayers of polystyrene−poly(2-vinylpyridine) block copolymers on silicon surfaces were utilized as structural elements for the production of parallel metal nanowires. Metal ion loading of the P2VP block with simple aqueous solutions of anionic metal complexes is accomplished via protonation of this basic block, rendering it cationic; electrostatic attraction leads to a high local concentration of metal complexes within the protonated P2VP domain. A subsequent brief plasma treatment simultaneously removes the polymer and produces metallic nanowires. The morphology of the patterns can modulated by controlling solution concentration, deposition time, and molecular weight of the block copolymers, as well as other factors. Horizontal metallic nanoarrays can be aligned on e-beam lithographically defined sil...

Using cylindrical domains of block copolymers to self-assemble and align metallic nanowires.

We survey the chemical reactions between common precursors used in the synthesis of metal chalcogenide nanocrystals and outline how they affect the mechanism and kinetics of nanocrystal growth. We emphasize syntheses of cadmium selenide and cadmium sulfide where a variety of metal and chalcogenide precursors have been explored, though this is supplemented by studies of zinc and lead chalcogenide formation where appropriate. This review is organized into three sections, highlighting kinetics, metal precursors, and chalcogenide precursors, respectively. Section I is dedicated to the role of precursor conversion as a source of monomers and the importance of the supply rate on nanocrystal nucleation and growth. Section II describes the structure and reactivity of cadmium carboxylates, phosphonates, and chalcogenolates. Section III describes the reaction chemistry of commonly employed chalcogenide precursors and the mechanisms by which they react with metal precursors.

Ralph A. Zingaro

Papers

THE EXTRACTION OF IRON(III) FROM ACID PERCHLORATE SOLUTIONS BY DI-(2-ETHYLHEXYL)-PHOSPHORIC ACID IN n-OCTANE

Phosphine oxide—halogen complexes: effect on p—o and p—s stretching frequencies1

Infra-red absorption spectra of eleven arsine sulphides from 15 to 30 µ. The as—S stretching frequency

Some Phosphines, Phosphine Sulfides, and Phosphine Selenides.

Infrared studies of amine—halogen interactions1